URGENT!! Platy has a bump on head!

[aerofish]

A red-wag platy i got a couple weeks ago had this light brownish bump on the top of his head. I didn't think much about it until today. The bump is now on the right side of his head (just behind the eye). There is no more a bump on the top!

what is this??? and what should I do? Will it spread??? Will it infect my other fish?

 

[GP]

We need to know the tank size, tank parameters, how long have you had the tank cycling for, how long have you had the fish for, and possibly some pictures would help.