About a year ago I had mosquito bites. The marks are still there and have become a dark circle of about. 5 cm and with light skin inside and dark centre again. Recently I had a minor scratch on my feet which turned into a infection and I have a similar b

Those darn Skeeters. You reaction to mosquito bites is more than likely part of what is known as "Skeeter Syndrome". You boy has an exaggerated response to a protein in the mosquito's saliva. I think the scratch incident is coincidental and not related to the bites.
Need more info. It's hard to diagnose skin problems without seeing them. Please make an appointments with your family physician and/or a dermatologist.
Plhyperpigmentation. You evidently have a skin type that makes extra melanin (coloring) in response to inflammation. It will fade with time, but you should avoid sun and see a dermatologist for other ideas.