Welcome and thanks for posting your query to HCM.
After reading your query it is too early to make a pin point diagnosis as you have not mentioned your age and side of appearance, even then we can make out two possibilities:
zoster: If the lesions are on the same side then there is possibility of this problem which is actually a viral infection by herpes virus causing unilateral appearance of blisters with pain in it. If you are young adult then this is not a thing of worry but if you are post 40 years then definitely need antiviral
2. Contact irritant/allergic dermatitis(CID):It appears due to contact with some allergic or irritant material. Though according to you have not done anything unusual so possibility is less.
For the time being keep a watch over the lesions if they increase or become large in size or painful then you must consult a dermatologist
who can prescribe you the treatment accordingly. Till that time you can do cold
compressions for multiple times a day and can apply very thin layer of calamine
lotion. Do not apply anything having irritant potential- and no self medications.
Hope this information will be helpful.
Dr Sanjay K Kanodia
MD ( Dermatology and STD/ Venereology)