My Dwarf Guarami has something growing

Ok.. for the past week i have notice something wrong with my Dwarf Guarami.. there's like a ulser or something growing on the body. the top thing on the picture right now you can actually see thru.. I'll try to get a more recent picture.. I just don't know what it is, so i could cure it, if it is possible. the fish has the same energy, eats good and don't act like there's nothing wrong

The middle one is alot bigger today.



Can anyone tell me what it is? and how i could cure it, if it is possible.

every input counts... I don't want to loose him!!

Thanks

Thanks,
I'll give that a try