Not Sure How to Help My Betta

Hi everyone, Im currently worried about an injury/disease my betta has and Im really unsure on what to do. My betta lives in a 5 gallon, heated, cycled tank and Ive had him for a few months at this point. A few days ago I noticed a white mark on the base of one of his fins. I thought it might heal itself but it hasn't and I cant figure out what it is. It could be white spot but theres only one and when I look up close as it it seems swollen and theres a purplish colour around it. If anyone has any idea what it could be please let me know. My betta has been a bit quiet today but is still able to swim, eat and is attentive.

Ive attached photos below as well as the medical products I have for him. My town is currently surrounded by bushfires so getting other products is tricky but if none of these medicines will help I can at least try to get something more useful. Thank you

My betta has begun not using his fin that has the injury on it. Hes keeping it clamped against his body not. Please does anyone know what to do?

I'm going to start off by saying I've not seen this before, so if anyone more experienced comments, feel free to go with what they advise.

I think it's been mentioned the -fix products damage their labarynth organs. Is that bathing salt the same thing as aquarium salt?

My usual place to start with illnesses I haven't encountered before is aquarium salt 1g per liter (or people on here say 1 tablespoon per gallon), indian almond leaves and methalyne blue. I usually do a 50% water change right before adding all of this.

Are your water parameters ok?