jaguar cichlid health concerns

Hey everyone
I recently was given a 12 inch jag cichlid.
He is in a 125 all alone for about 2 days now.
He isnt really eating much.
He chased a goldfish but put in a half ass effort
He eats the cichlid sticks i offer but he doesnt ingest it all and sometimes spits it all out
I threw a couple silversides in there they r juat drifting on the bottom.
Could it be he is sick? Parasite?
Or does he just need some time to get used to his new home?
Only visible issues are his side fins they arent torn up but they open n move like an accordian if that makes any sense lol. They look brittle and unhealthy. Everything else visibly seems okay

Any opinions, advice or suggestions it would be greatly appreciated

I got him for free he does or did have hole in head at one point could that be lingering? Ill def keep lights dimmed he doesnt really act sick lol

Pic of fin

Its a new set up but its been cycling for weeks had some danios in it for a couple weeks to help cycle. All lecels r good. This fish came to me sick i think. There is a hole in his head but i dont kno if its a scar from the disease or if the disease is still there. Should i treat for hole in the head to be sure?

Can metronidazole be pruchased at any aquarium store.