Is it just you who was sparring quite a bit out of your weight class or were quite a few fighters doing it? I've probably been training about the same time as you and have sparred plenty now, but wasn't allowed to do so until I'd proved I was capable and ready. I have sparred with the weight difference around 11kg but the other fighter is well aware not to load up or go hell for leather. We are usually out in that position to work on something. Usually the heavier guy is a lot taller than me so it's to work on getting inside and working whilst for him it's working out of a corner or off the ropes once I've got inside. Keep at it but if it's that type of club where there's a lot of heavy sparring for little benefit and the emphasis isn't on working on something to benefit you find another club.
Your 2nd session will be better, the first time I sparred I went in with my best mate. He had been boxing for 2 years at the time, id been doing it 6 months, I was about 80kg and he was 64kg, I completely gassed and he busted my nose up 2 days before our holiday haha. You'll be fine once you step back in, your confidence will build gradually.
Get a facebar headgear and dont take any **** if the guys gloves arent 16oz or are but the padding has worn out or is hard as a rock. Also tune the guy and let him know he acted like a dick, he didn't do it "accidentally" he knew the situation full well and still went full blast even if he outweighed you and he went at a higher intensity than you were boxing at. He'll feel bad about it might even apologise and you could still have a productive spar with him in the future. Otherwise **** it simply refuse to spar the guy anymore.
Don't be put off by a bad experience in sparring. There's days you get in there and you'll take a bit of a pasting and there'll be days when you feel like no one can touch you and you can't miss. You're not a pro, so it'll happen. The most important thing with sparring is it's about learning, not fighting. If someone's got a weight and experience advantage on you they shouldn't be loading up and looking to prove a point and when you get more experienced you should remember that when you jump in with someone new. At this stage you're probably better off getting in there with someone you know and you're comfortable won't take the ****. Get your confidence and then start jumping in with different styles and sizes so you learn. I wouldn't get down on one bad experience. You might have come away from it feeling shitty, but I can assure you the bloke who dished it out learnt nothing and if he carries on looking to make himself feel big by putting it on someone who's never been in before, he'll come unstuck soon enough when someone does the same to him.
You always have to look on the bright side and turn what was a negative into something positive. Every gym is different and you may not agree to what a trainer's methods are, may even feel unsafe or unjust, but you might learn something out of it. You already know what a bigger opponent's power feels like so you'll know what to expect next time if you do decide to spar with him again. In Mexico I was 12-13 yrs old sparring with 30 somethings outweighing me from 20 to 50lbs, about 10-20 kilos. Got my ass kicked the first time, but I held my own and kept going back to the gym until I learned to stick and move, attack the body more, and systematically break a larger opponent down instead of trying to knock their head off with one shot. Many times its hard to find someone your size you have no choice, but to practice with someone bigger. You can talk personally with your opponent to take it all easier on you, do more CONTROLLED SPARRING than full contact sparring. Controlled sparring you can work on your skills more before actually doing full contact, but like someone else said, all gyms are different, some may want to see what type of character you bring. Have fun in there man, just stay safe and keep those hands up! Don't be nobody's punching bag! Also, NEVER stand in front of a bigger fighter, use a lot of lateral movement to get out the danger zone and get to him using angles. When you shadow box or use a mirror practice your combinations until you really don't even have to think about throwing, you will just react naturally and know when to counter. Learn the most knowledge you can get and practice whatever makes you most comfortable. You'll receive your lumps as well as give them. When your hard work pays off you'll learn you can do things you thought you couldn't. Put on a boxing clinic or drop someone like a sack of potatoes, you can surprise yourself. Godspeed.
Its good to be scared of going back in the ring in some ways because it makes you respect the sport in its reality. I think it would be best to spar again and belive in yourself. This sport is for some people and others dont quite fit into it