I went on vacation and unfortunately the person I trusted to take care of my fish left the light on for a week and that caused him to but his tail off. Which then I believe turned into fin rot. I treated with API aquarium salt for 10 days. I did a 50% water change everyday and did the salt treatment and that seemed to help. However, I came home today and there’s a white pimple like abscess on his head when it wasn’t even there this morning.he has no other spots so far and he’s eating well and not scratching himself on anything. He doesn’t really swimm around unless I walk up to the tank tho. 
Other information
He’s by himself in a 5 gallon, I do a 25-50% water change every week where I vacuum the gravel.I use aqueon water conditioner.he has a heater and a filter. I feed him pellets and freeze dried blood worms.
Water parameters
Nitrite 0ppm
Nitrate 0ppm
pH 8.0
Ammonia 0
Temp 78°
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Aubrye Rae
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2What is your question? What to do? What is wrong with the fish? Please edit to add your question. Please also add the water readings of your tank as I am sure the fish experts will be curious about it :) – SerenaT Oct 14 '21 at 15:49
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Not an answer because I'm not sure about Bettas, but I've seen white lumps like this on a goldfish with a "wen". In that case, it was just where the wen was growing and it lasted a long time (months-years) with no obvious ill effects on the fish. In the photo, I'd say his back looks less than straight. Is that normal or does it make him swim inefficiently? And lastly, is pH8.0 ok for Bettas? Otherwise your water parameters are great. – Pam Oct 29 '21 at 14:04