This looks like a painful corn/wart or localized thickened skin due to repeated friction/trauma, especially since it is on the corner of the thumb and keeps getting hit. It is not related to any
vitamin deficiency.
Next Steps
• Avoid repeated trauma (be careful during household work)
• Keep the area moisturized during the day
• If pain is significant or not improving in 2–3 weeks, visit a dermatologist for removal (simple procedure like cautery/cryotherapy)
Helpful Tips / Word of Caution:
• Do not cut or pick the lesion yourself
• If it increases in size, becomes very painful, or shows black dots → consult earlier