They may be consumed up to the use by date. Unopened deli meats generally keep for two weeks. However, once the package is opened, the use by date is meaningless; the meat should be consumed within 3-5 days. This is because anti-oxidative gases that preserve pre-packaged deli meats escape from the packaging once it is opened. Unopened packaged deli meat can be frozen for one to two months.
Chest soreness that is caused by working out used to be attributed largely to the buildup of lactic acid, which is a waste product created by the muscles when strained.
It sure can, though any time you're having these kind of symptoms it's best to get it checked out by your doctor. Chest pain may be caused by cardiac issues, muscle strain, or acid reflux, though only a doctor can tell the difference, but any sort of chest pain should be checked out immediately. Here is some information you may want to review in the meantime.