What could be the cause of severe burning in the inner tissue of the ankle?

Nerve: This could be a neuropathy or issue with the nerves in your ankle. They could be impinged at the ankle, at the knee, or in the low back by a bulging disc. Or, if you have a condition like diabetes, it can cause this, but usually on both sides. Doct.

Tarsal tunnel: Sounds like a classic tarsal tunnel syndrome but there is usually a medical cause ie low thyroid, leg swelling, trauma, arthrisits etc.

Nerve or tendon: This could be nerve irritation on this area as burning pain is often from the nerve. But this may also be tendinitis or degeneration. A period of rest and good supportive well cushioned shoes is a good start but if pain persists or worsens, see your doc.

An entrapped nerve: There is a condition called tarsal tunnel syndrome. You may have this.