Such pain is pleuritic, and establishing the etiology, or causive agent is sometimes difficult. Costochondritis i one possibility, In general, such pain is self-limiting, and will subside after several days. A common cause is a viral infection. While it may be cause by straining, this if often not the case. The pain develops in the sliding pleuritic surfaces. Rest is esential. In a worst case scenario, one lung may collapse, which is why rest is so important. In general I would see a physician in an ER upon developing such pain. It is definitely not cardiogenic in origin, so that is one good thing. There is very little to do for a viral infection except monitoring, rest and vitamin C. Ant-viral meds are ocasionally used, but the literature regarding their efficacy is inconclusive. Every once in a while there is a bacterial infection, which will generally be acompanied by a fever. In such a case anti-biotics are used. Yes, this could be relayed to your viral infection called a "cold", which is caused by a virus.
When I gave birth to my first child, the strain was so hard on my body that the cartilage on my ribs got hurt. I have what is called costochondritis. If the pain doesn't go away, you should look into it.
Any type of exercise that you decide to do for the first time should be done slowly. Always do warm ups and body stretches before you start doing any type of exercise. Start off with a short duration time and build up gradually as your stamina increases.
It is likely that you have overexerted and have a muscle problem due to the sudden exercise. As you have had it for 5 days and it not getting better, I would suggest that you see your doctor.
In the mean time, take pain relief medication as directed on the packet and have warm relaxing baths.
The muscle problem will be unrelated to you having a cold virus.
If you do notice any urine problems like cloudy urine, pain or soreness whilst urinating or afterwards, make an appointment to see your doctor as soon as possible so that he can check you out for any urinary infections.
Wishing you a speedy recovery.