My friend's Red-ear slider has a prob

[SulcataTort102]

Hello sup everybody.
My friend owns a baby red ear slider that is still quite small.
But now,it has a boil, like the size of a facebook emotion.
Tell me three things i'm not sure of:
1.Are these about terrestrial turtles?i might be on the wrong forum.If so,help me anyways.
2.How did the boil on my friend's turtle neck appear.
3.Most importantly,how to cure it?
Please be quick .

 

[kathyth]

It would be very helpful if you could post a picture of the " boil"