I guess the options are
1.Subcutaneous nematode
2. Bacterial skin infection
3. fungal skin infection
4. cancerous tumor
5. Benign tumor
If you lance it, subcutaneous nematodes are easily seen. Bacterial and fungal infections would require you to culture the lancing, however these are less likely in a single legion as they tend to spread quickly, and you could just routinely treat it with a topical antibiotic, I would recommend a sulfur based one. If you suspect four, your better off leaving it alone as you risk releasing cancerous cells into the blood where they can spread.