Better to get it excised

This is delayed healing ..ulcer is in healing stage ,if you are not having fever /pus discharge,then don’t worry it will heal ,give rest to the joint ,and check sugar (to know the diabetes status),viral markers . If you are very anxious about joint status,get an x ray of hand .take vitamin C , apply local antibacterial ointment

Surgical Excision is complete Curative procedure for it

Based on the serial images, the wound appears consistent with expected healing after thermal cautery with a superficial necrotic eschar/slough formation. There is no obvious evidence from the images of a retained vascular root or incomplete removal, although a residual lesion cannot be completely excluded without clinical examination (dermoscopy/palpation). The yellow/white material is more suggestive of fibrinous slough/autolytic debris during wound healing rather than definite infection. Clinical infection would be supported by increasing erythema, warmth, swelling, pain, purulent discharge, foul smell, fever, or spreading cellulitis. Given the location over the joint and the current appearance, conservative wound care is reasonable if there are no infection signs. Avoid repeated cautery/trauma at this stage. Keep the wound clean, use gentle saline cleansing, maintain a moist healing environment, and monitor progress. Surgical excision should be considered if there is persistent lesion tissue, recurrent bleeding, progressive growth, failure to heal, or suspicion of deeper involvement.