Suggest Treatment For Welt On Spine From Neck To Mid-back

I have a welt about 2 in or so long that runs horizontal right across my spine right in the middle of my back. It seems to have appeared out of no where because the area hasn t been hit, nor did I feel like I got bit. It doesn t hurt, but feels a little weird, which is what got me to feel back there and find it. Any idea what might be the cause and is it something I should be worried about?