Is it possible to use the neti pot if I have a perforated eardrum?

Should be fine. Neti pots (saline irrigations of the nose) are pretty benign (not too much risk of harm). Go ahead and try it. You could notice some water come out of your ear with the perforation, which is generally ok. There is possibly a risk of ear infection. (especially if you get infections with swimming). If that happened, you'll have to treat it, and stop the neti pot.