The lesion between your toes appears to be a plantar wart (verruca) which can become painful due to pressure and friction.
Next Steps
You can try over-the-counter salicylic acid-based wart treatment. If no improvement in 2–3 weeks or pain worsens, consult a dermatologist for cryotherapy or chemical cautery.
Health Tips
Keep the area dry, avoid walking barefoot, and don’t pick at the lesion to prevent spread or infection.