M.G.
I have a lot of experience with 'knots'. The best thing for me is something my PT suggested - a have an old soft tennis ball that I prop up against the wall. I lean against it on my sore spot (mine is kind of wedged in behind my shoulder blade). I lean against it with varying degrees of pressure and keep it there until I feel the pain subside.
What it does is bring blood flow to the area and this helps 'heal' (I think?) the area. It's kind of what massage does.
Some people do this laying down, but I prefer to be upright.
The key is to hold it there until you kind of don't think you can take it any more (the pain) and then suddenly, the pain is gone. It releases.
I personally, don't like the idea of having someone I don't know show up at my house, especially with kids at home. I would if someone could recommend them personally maybe, but not just off the internet.
I have found that OTC stuff for your back/shoulder really is effective also for the odd strain. It's not supposed to be addictive like prescribed muscle relaxers are. That will take care of a knot for me, and then I don't keep re-agravating it.