What Causes Pimple Like Blisters In Inner Thigh?

Hi,I have 2 red,pimple like blisters/pimples on my inner upper leg area.They are a little smaller than an eraser head in size.There are two other very small ones clusterd close by.No pain or itching.Had them for over a week.They don't seem to want to leave.Getting a little nervous.Any ideas?Thank you.