Blisters on the side of my foot

I have what looks like recurring blisters on the side of my left foot.  The first time I got one I thought it was because I had been wearing my boots without socks.  It was very irritating so of course I popped it only to find that my foot never did go back to normal looking. I now have dark red spot on the side of my feet.  Not attractive!   Today I discovered another blister on the same foot almost a couple of months later.  Its irritable and I can tell has fluid in it.  What is the world is going on?  Should I be concerned?  

[Dr_Aparna]

Hi,
Foot blisters are a common occurrence for many people. The blisters are usually formed by friction, heat and sweating. There are a number of preventative measures that can be taken to stop these painful foot blisters from occurring.
One of the most important factors is the type of shoes you are wearing. The shoes you wear may be causing the foot blisters to appear. Your shoes must fit correctly to prevent blisters from forming. Shoes that are too tight or too loose can cause foot blisters. Also remember to check the inside of the shoe for worn areas or seams which may cause friction against the skin while walking.
Using some form of powder before putting your socks on can help to keep the feet dry. Using talcum powder, cornstarch or foot powder is an excellent way to avoid moisture in the foot area.
There are special lubricants, sprays and creams that specifically prevent the occurrence of foot blisters. If you find that blisters are appearing at specific spots on your feet, applying these treatments prior to walking may help keep the blister from forming. These treatments can usually be found in drug stores and shoe stores. They can be used as a preventative measure to cushion the area where the foot blisters occur.
ref:http://www.wisegeek.com/how-can-i-prevent-foot-blisters.htm
There is no need to be unduly concerned. Alternatively they could develop due to allergy, in which case oral anti-histamines will work well to treat them.
You should never pop blisters because you could cause them to get secondarily infected.