What bit me??

After a day spent mostly at home yesterday (I did do some chores outside around the house as well) I woke up this morning with a massive itchy welt on my leg. I’ve never felt something like this before. It extends the full length of hamstring, has been itchy for about 6-7 hours and feel ‘hard’ and stiff whenever I move it around.

Any idea what Ottawa pest could do this to me?