Hello, Welcome to HCM. I understand your concern. You have lymph node enlargement in your armpit due to horsefly bite on your hand. It might have been infected a bit. It s good that you took antihistamine which will help relieve the allergy. Continue the same till swelling subsides. You need to take care of wound by topical antibiotic cream like betadine along with topical steroid cream like betamethasone. You should also take oral Ibuprofen to relive pain in armpit and inflammation. Wash the area with mild soap and water and apply these cream 3 times a day. You need visit local GP to get these medicines. The pain and swelling should go away in a 2-3 days if properly treated and not infected further. Hope this will be helpful. Do ask if any further question is there. Take care.