You should get your running form checked.
Agree with comments about running style. Heel strike is a good path to injury (for most people). Midfoot strike is safer and will stop you pronating or supinating if that is part of the problem.
You should be running with chest out, up straight and your front foot should strike on the midfoot under your centre of gravity, not out in front. Kick up and back (the old "kick your bum").
I posted a really good slo mo vid of usain bolt's style on the Thread about Running. it's a perfect vid of great form - check it out if you have time.
Orthotics might be the answer but (in my own experience, having ditched them ages ago) if you switch to midfoot strike, you won't need them and they'd only be an impediment when running.
If you're getting this from rugby training, I'm guessing you're already running on a softer surface like grass or a track, so that is unlikely to be an issue (concrete is the worst, avoid footpaths).
Definitely get your running form looked at if you can and check if you have the right shoes.