Chapman was forced to go to hospital after burning his nipple by pouring hot milk over his chest.
Wilder admitted that the incident is the strangest injury debrief he has ever received.
He told the Daily Mail: "Adam Chapman, like the good dad he is, was making his baby some milk and he managed to shake the bottle up and down, but he didn't put the lid back on properly.
"He burnt his chest and had to go to hospital for a check up.
"He's burnt all his nipple. It's an unusual injury, but he's managed to play the game. We talk about injuries and that is what I have to go through in this job."
The 22-year-old was able to take his place in the Oxford starting lineup and helped United beat Wycombe Wanderers 3-1 to climb to 15th in League Two.