My 3 year old slammed the toilet seat on his penis what do I do?

My 3 year old had been potty trained standing up for about a year now. we haven’t had any issues with him playing with the toilet seat until a couple of weeks ago where he would play with, and slam the toilet seat a couple of times. I always tell him to stop playing with it, as it can hurt him if he keeps it up and ends up dropping it on himself. well yesterday it happened, my mother in law was watching him and she said he told her he needed to go potty and so he went like normal. Usually when he goes he doesn’t want anyone in there with him and he wants the door closed but cracked open a tiny bit, so thats what she did and waited by the door for him to get done. she said while she was waiting she heard him get quiet so as soon as she opened the door she saw he was playing with it, as soon as he locked eyes on hers he slammed the toilet seat down on his penis and started screaming. she said when it first happened his tip did swell up to the size of a thumb and the whole tip turned blue, and he said it hurt him to pee. but this morning it is back to its normal size and color for the most part but it left a nasty looking bruise on the side of his head, and it doesn’t hurt him when he pees, but he said it feels weird when he touches it. do I take him to the pediatrician for something like this to have it looked at, or just leave it be? On The plus side, he did learn to stop slamming the toilet seat and playing with it.