red/white spot on face!!

[freemn8r]

Hello everyone - a little advice would be appreciated

My betta fish has had 1 white spot, red outlined, on his blue/red body. It kinda looks like a pimple!! Been there for a little over a week and a half now. He is still eating fine and moving around fine... no other signs of a problem. I have no idea what this is.

Background:
he is a VT betta fish (bought from wal-mart over 1 year ago) that was being kept in my 10 gal aquarium (cycled), gravel, water has tested to be neutral, i keep aquarium salt in it and it is roughly 78 degrees/room temp, filtered. Fake plants and a lil decor. Well, about a month ago I changed the filter (did not rinse new filter before putting in, box said i should have)...

Currently:
when I first noticed the spot I moved him to a clean 1 gallon tank and began doing a lot of water changes - also began using some mellafix and extra salt. Today I gave him a 25min epsom salt bath and then gave him100% new water in the 1 gallon tank. I added some indian almond leaves as well. The spot looks A LOT of better than it did a few days ago.

My question is - what was the weird pimple looking spot? could the 10 gallon tank still be infected? I admit there had been a slight build up of uneaten food at the bottom (not bad, but noticeable, What i cannot get w/ the net)... Any advice would be appreciated.

[Fabian]

Does the 'pimple' looks like it's a bump?
It could be tumor.Or parasite infection.
If your betta seems to recover with those methods,do it until it fully recovers.

[freemn8r]

it was a red bump w/ a white center... now it (thankfully) is just a fading red bump (he has a blueishredish body). I think he is getting better - prob was an infection of some sort - I cleaned out the 10 gallon tank and it had a lot of hidden trash down in the rocks - might have been a lot dirtier than I thought.
Appreciate the response!