Skipping a semi long run?

The plan for today was to go run at semi long run, 18km was my long run for this week. This is a rest week so the long run is not as long, or longer, as last week. I got up at 5AM ready to go out and run just to realize that my left foot hurt. I guess that I hurt myself running bare foot yesterday in or out of the transition zone.

This is weird, it's like I have a bruise under my heel, not pain other than that. But believe me running on a bruise is probably not fun, so I decided to skip it ... for now.

Now I am wondering, the rest of my week is already full of running, should I run this longish run and skip a shorter one. Or should I just go as if I did it and forget about it.

Or maybe I could change my entire running technique and start that forefoot landing that everyone talks about ;)

Seriously I will see how it goes, if I feel better tonight I will go run it, if not I guess I will just forget about it. Which I really don't want to do though.