Looking at the ulcer and other parts of your mouth. It appears that you chew pan masala/ tobacco or may be smoking as well. What your mouth looks like currently,  provisional diagnosis is OSMF( oral submucous fibrosis) , there are fibrous bands formation under the cheek layers. Which leads to difficulty in opening mouth fully and mouth opening would reduce from 3 vertical fingers to less  You can start Antioxidant : MINTOVIT- L one tablet daily for a month and get it checked with a specialist.

Hello Sir. It is difficult to confirm what is the cut spot with the picture. But there are other things that also need attention here. The rest of your mouth in the photo does not look healthy. It would be better to get a dental checkup done.

Cheek biting??? Poor oral hygiene. Go for scaling and polishing

Hello Ths is traumatic ulcer .nothing to worry about it.but ur mucosa not look healthy

The cut is not a serious problem but your mouth does not look healthy. In case you have any habits like smoking or tobacco chewing please stop them! If the cut does not heal you should immediately visit an Oral Surgeon.