Does not look serious to me.
Spray some WD40 on it, let it sit on there a few minutes, then scrub it with an old toothbrush or similar to get it to where you can tell just what you have got.
I think it's OK, clean it well to make sure.

 

Looks like Tar!! Try to clean it off. JR

 

I agree, it looks more like tar. Sure doesn't look like a crack the way it curves around at the top as well as the shape. Looks like a drip run in the middle.