Check the other side for a similiar “thing”… if theres nothing over there… thats its anus ???… it would b on one side only, right behind a back leg as uve pictured. Havent figured out if there b holes are on a certain side per species or the same side every time… but i do know for sure thats where there located. Most “new” lung owners go through this problem. Dont b pokin it with a q tip or applying medication if thats the only “marking” behind a leg on one of its sides…