Running Pains?

Monday at lunch hour I went for a run to week 2 day 3 of couch to 5km. It was quite a warm day and I had some struggles with 90 second intervals. A colleague at work Informed me that I may be starting out too quickly and then burning out early. He said I should try to jog and keep it slow for the first few minutes.

Last night at about 8:30 I had the urge so I harnessed up my dog, River, and we went for a long run. I ran 3 minute intervals and did week 3 day 1 twice. It felt really good to be able to accomplish that, an also to give River some well deserved exercise. We got turned around and lost in our own community; it's still developing, so we don't know it all yet. Good thing that I had my iPhone with me and used the map to get home.

I've been noticing chest pains in the past few days. They seem to be uncorrelated to working out as when I've been running they don't bother me. When I try to stretch I can't seem to get it loosened. Are there chest stretches? Can you pull a muscle in your torso by running?