Crap man, I had just fed him some pellets. Would that be ok? I heard that kind of overfeeding him would make him more likely to throw it upI think the best course of action is to wait and see, since the suction cup is deep in the fish's digestive tract and any intervention to remove it would probably cause more harm than good. RTCs are tough fish and don't die easily, in all likelihood it will eventually pass the cup.
I'd avoid feeding it for a few days, since the addition of more food might cause an impaction. You can feed him some roughage (e.g. algae wafers or blanched veggies) afterwards to help him pass the cup.