Stretchy scab, now a hole in my arm

I have an odd concave lesion on my upper arm. It just showed up one day with a scab over the top. When the scab started to fall off I went to remove it, however, when I went to pull it off, it was stuck with this stretchy stuff. No matter how much I pulled it, it just kept stretching and the scab wouldn't come off. I had to get some scissors and cut the stretchy stuff just to get the scab off. What is the stretchy stuff? After that the sore dried out and formed another scab, one without the stretchy stuff and fell off on its own. Now I have a sore, red, crater type thing on my arm that won't go away. What the hell is it? I don't know if I should investigate the hole in my arm to see if the is anything further in it, or whether it will make it worse.