Hi, The rash appears to have been caused due to the hike. The area is tender and warm which makes it look like skin inflammation. The most probable cause could be a tick bite. Other causes could include exposure to any allergen from bushes or plants or some other insect bite. You need to examine the area for tick still present and if seen then you can get it removed with a tweezer. Wash the area with soap and water thoroughly and apply antibiotic ointment over the area. Also, application of antiallergic ointments containing antihistamines like diphenhydramine which you can find over the counter. It would help in reducing the swelling and tenderness. Pl visit your physician if you develop fever. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Anoop Kumar, General & Family Physician