I have some excess tissue inside my mouth near the cheek, it looks a bit like a small skin tag but is really uncomfortable. Should I see a dentist or a doctor for this? What could it be?

The excess tissue inside your mouth, resembling a small skin tag, could be a benign growth such as a fibroma, mucocele, or a traumatic fibroma, and it's recommended to consult a dentist or an oral surgeon for a proper evaluation and diagnosis, as they can assess the tissue and possibly remove it if necessary