if u have a tear you'll know about it soon enough. get ice on it as much as you can for as long as you can, completely immobolise and get the doc and mri asap.
certainly sounds like a tear to me. you wont nec see any change on shape..and tears can occur at either end of the pec, and even along its length. most tears wont cause a change of shape actually unless you've really ripped that sucker off a tendon or tendon from bone or done a major tear, and id think you'd be in agony by now.
those are usually the ones that bruise also.