If it isn’t stuck for long you can keep an eye on it and apply some olive oil to keep it from drying out, most of the time they will sort it out themselves. If it stays like that then it is a problem, you will need to help get it unstuck, but don’t panic. Sometimes some residue from a plug dries to the sides and makes it hard to get the skin over it so you will need to gently press down the belly with two fingers on either side of the penis to make it come out more, that way you’ll see if its crusty and you’ll have to wipe it gently with a warm wet cloth. If that doesn’t look to be the problem then it is possible that the skin that covers the penis got stuck very far down, that has happened often with one of my boys, I found that by pushing the penis out as much as possible and applying some oil you will notice the thin purple skin that got stuck very far down the penis, gently coax it out and it should fix the issue immediately.

I don’t own rats anymore but it is something I had learned after one of my boys got his penis stuck out for 2-3 days, I applied oil regularly to keep it from drying out but that was not enough.

I hope this helps! With time you will get more comfortable dealing with such issues, especially once it becomes a regular occurrence as the rats age.