Betta With Funny Lump

Hi

My Betta has a funny lump on his side and I'm not sure what it is. I have taken a pic with my mobile but it's not very clear and I can't upload pics from the proper camera til tomorrow.

He is in a 4 gallon tank on his own and water stats are ammonia 0, nitrite 0 and nitrate 30. I change about 30% water every week. I have had him for about 4 months and he is fine and nothing has changed in the tank.

I check him properly every day when I feed him and he is so nosy he is out and about all the time watching what's going on around him so I see him all the time. I didn't notice the lump until this evening though so either it was very small yesterday and I didn't notice it or it appeared quickly today.

He has been constipated before but it didn't look like this as the lump is vey pronounced (small pea size) and ONLY on one side of his body. I am bit bothered because it is so pronounced the scales on it seem to be standing up and I know what that means..... He's not doing anthing else different though and is behaving absolutely normally and there is no sign of strange poo. I am going to feed him a pea now just in case but has anyone got any ideas in case it doesn't help?

Thanks

Is thelump soft filled with fluid or hard.
I would still try a bacterial med on the fish.
Good luck.

Looks like it may be a internal Parasite or maybe bacterial infection not sure though just a thought.

Thanks for the replies.
Lump looks hard not filled with fluid - just as though there is a pea under his scales...... but what does that indicate?
Also any recommendations for treatments?
It's very bizarre as everything seems normal otherwise and he seems fine. how quickly can something like this come on and how serious could it be??

It could be a tumour then if its hard.
Don't know your location for a med, but if it is a tumour sorry the bacterial med will do nothing, but its worth a try.

OK Will try a bacterial med as got nothing to lose Fingers crossed it might do something... Any recommendations for which one? I'll go to Maidenhead Aquatics (am in UK) tomorrow to get whatever I can. God, it seems to be the week for it - we lost one family cat last week to a bump we think and another (15 yr old) is looking really poorly at the moment.

Sorry R.I.P.
Anti internal bacteria med by interpet.
Good luck.