Thanks for reaching out about Tuktuk and including a photo. The foot appears to be infected. Is he housed with another turtle that could have bitten him? Or another type of wound. Water quality needs to be pristine to prevent further infection. Floating with one side dependent is often a sign of a congested lung, i.e. pneumonia. A veterinary visit is highly recommended as soon as possible, as systemic antibiotics are probably needed. Check and correct all husbandry parameters including water and basking temperatures, nutrition, and UVB exposure. Good luck.