My 5 month old son bumped the back of his head on the left side when he rolled over. He hit the plastic toy thing that holds the little toys up for kids to grab (if that makes any sense). He didn’t cry he just looked at me really surprised. I check the area and it was red (not anymore). I can’t see or feel a lump and either can my husband but his head is pretty odd (he’s getting a helmet soon) he hasn’t fed yet but he played after and just went down for a nap. Should I be worried?