It's swollen and hard from bug bites.

Insect bites are red and hard, which is usually caused by insect bite dermatitis. You can go to the dermatology department of the hospital for treatment. Insect bite dermatitis can be treated with antihistamines such as diphenhydramine and chlorpheniramine, or calcium lactate and vitamin C. Attention should be paid to the cleaning and care of the affected area at ordinary times.