Hi~
I would, as the other person said, see a dermatologist right away. I'm not saying that to scare you, abnormal moles are quite common on some people, such as myself. I'm 28 years old, and I went to see my dermatologist a little over a year ago because I actually had a small mole on my back that was disappearing. While he said that was completely normal, he noticed another one that I never really checked out that well because I couldn't really see it.
I had it removed right there in his office, a procedure that takes 2 seconds and is completely painless, and he sent it out to be biopsied. Now I'm not saying this to scare you, just to share my experience. It saved my life going to the doctors that day. My biopsy results came back as an 8 on a scale of 1-10, 10 being Melanoma. I had to go back in for a more in-depth surgery, they removed about a 2" area of skin on my back and got all of the "damaged skin" to make sure it was all gone. I've since had 3 more surgeries, having a total of 5 moles removed. Three came back as 8s, one was a 5 and the last was completely normal.
My experience is also based on the fact that I started going to tanning booths when I was 14. That plus the countless hours I've spent outside in the sun since I was a kid has brought me to this point. I've been 'tan-free' for almost 2 years now, and my doctor has explained to me that a lot of the moles I have on my body now just look abnormal and not to worry. But I have to go see him every 6 months to see if anything has changed.
When you go see your doctor, he/she will take a photo of the spot you're concerned about. That way each time you go back he/she can tell if it's changed at all. That should be your first step. But if you do have to have it removed, don't worry...you'll be fine

For me it was better to be safe than sorry. How old are you by the way? That's always something to take into consideration. Melanoma is more common in older people.
Whatever you do, please don't ignore it. No one but you is in charge of your health. Get it checked out and then you won't have to worry about it
Take care and good luck~
Melissa