Insect Bite Reaction: This is the most likely diagnosis given the patient's symptoms of a painful area with blisters following an insect bite. The reaction can vary from mild to severe and can include blistering, which aligns with the patient's presentation.

Contact Dermatitis: This could be considered if the blistering and pain are due to an allergic reaction to something that came into contact with the skin, possibly related to the insect bite or another substance.
Folliculitis: An infection of the hair follicles could present with similar symptoms, especially if the insect bite became secondarily infected.
Impetigo: A superficial skin infection that could result from scratching the bite area, leading to the introduction of bacteria.

Cellulitis: Although less likely given the absence of fever, cellulitis is a serious infection that requires prompt treatment. It could be considered if the area of redness and pain is spreading.
Erythema Multiforme: A skin condition that can be triggered by infections or other factors, including insect bites, and can present with blistering lesions.
Necrotic Arachnidism (Brown Recluse Spider Bite): While rare and less likely without specific exposure history, a brown recluse spider bite can cause severe skin necrosis and should be considered in the differential, especially if the lesion progresses or does not heal.

Leishmaniasis: Caused by the bite of an infected sandfly, leading to skin lesions. This would be very rare and typically associated with travel to endemic areas.
Myiasis: Infestation of the skin by fly larvae, which could present with blistering or boils. This is rare and usually associated with poor hygiene or specific exposures.
Scabies: An infestation by the mite Sarcoptes scabiei, which can cause severe itching and skin lesions, but typically does not present with blisters in the initial stages.