It looks like bumblefoot infection in both foot pads and inflammation of the skin on top. Scaly leg mites might also be a problem. I would start by doing a warm Epsom salts soak to his legs for 15-20 minutes a day. Bumblefoot may be treated with soaking, applying Betadine plus sugar (sugardine dressings,) Prid drawing salve, scab removal and squeezing out a pus plug, or surgery. Leg mites are treated by smothering leg mites with Vicks salve, sulfur powder combined with vaseline, Nustock cream, plain vaseline, castor oil, or other thicker oil. There are multiple possible treatments for each of those. If you can see a vet, they might even try an anti-inflammatory drug, steroid, or antibiotic.