Thanks for your query and the picture.
Noted the history of bite by an unknown bug/insect, itching, redness, tenderness, pain on long walk. Wants to know how to treat it and if it is serious or not.
All these points indicate that there is a severe reaction, I would advise you the following in such a situation:
-Take an anti-histamine like Cetirizine
-You may need prescription based treatment such as Oral steroids as you do not know the bug that has caused this.
-Try to restrict the movements as they may cause more spread of the allergen.
-Keep under observations of the Doctor too as it helps any other additional treatment like antibiotic, incision or dressing if needed in the future.
I hope this answer helps you, please feel free to ask for further relevant queries if you feel that there is a gap of communication.
These Q&A’s are for educational purposes and should not be relied upon as a substitute for medical advice you may receive from your physician. If you have a medical emergency, please call 911. These answers do not constitute or initiate a patient/doctor relationship.