I have two red eared sliders. They started fighting a while ago so I had them separated so one is in the tank while the other gets to walk around my room as he pleases and then they switch. They usually just sit under the bed. I went to check on one of them when I found this weird crack or something on his head. I don’t know what it is or if I need to take him to the vet or anything because he seems pretty normal and responsive. I know this isn’t from them fighting because this just happened and I check on them everyday, plus they haven’t had any contact in a long timethis is the full crack
It looks like a healing wound however the whitish film nearby could be an indication of a fungal infection. Keep an eye on the area and make sure it’s free of any debris and make sure the humidity and temp are within suggested parameters. It should get smaller. If the area or whitish film gets larger you may need to take the turtle to a vet to get medication.