Can anyone identify what’s on my betta’s left flank?

[On_a_dishy]

I’m posting this image here although I have another thread in the “new to the hobby” which is dealing with him and I’m getting some good advice.
If you follow the line of his left flank, about half way down there is a little gel-like substance with tiny white dots in it.
He is sick, and this was on him this morning. I have him a quick meth blue dip and it seems to have gone - but what was it?

 

[seangee]

Its probably slime coat to protect a little scratch. The advice @Essjay gave you is good. Fresh water is the best medicine. I have over 200 tropical fish and a dozen or so pond fish. I have zero meds in the house and cannot even remember when I last bought any. When I suspect anything is amiss my first reaction is a 75% water change - with another the following day. This invariably works. The little guy has had a stressful weekend, there is no point in throwing meds at him in the hope that you stumble across one that works. As @Essjay pointed out most meds do harm (and as a pharmacist she sould know). I woud not use meds unless I actually know what needs to be treated.

 

[On_a_dishy]

Thank you - I have done what @Essjay said and changed his water (50%) three times since this morning! He’s starting to show a bit of interest in his surroundings - God, he’s great 😊 Thanks for the reassurance!

 

[Essjay]

(and as a pharmacist she sould know)

Actually I am (or was, I'm past retirement age, and spent most of my life as a housewife) a chemist meaning I studied chemistry, not a pharmacist
[And my husband and younger son have doctorates in chemistry]

 

[seangee]

Actually I am (or was, I'm past retirement age, and spent most of my life as a housewife) a chemist meaning I studied chemistry, not a pharmacist
[And my husband and younger son have doctorates in chemistry]

Oops - that's what you get for growing up in a country where pharamacies are called chemist shops (me not you )

 

[Essjay]

We call them chemist shops as well and it does get confusing