My brushes are not making strokes

[Captain Fartbeard]

    My paint brush is not reacting properly when I try to make a line. When I try to draw a line it's stuck like this (see screenshot )   

  I think I might have unwittingly done something to make it like this but I'm not sure how to undo this. Is this a photoshop error or some feature I accidentially turned on? And if so, how do I undo this? 

[Captain Fartbeard]

Ok so I restarted my computer and it works fine now. Must have been a bug or something lol.