Iv just started working out. Mainly tredmill. I just have pain in thebottem left side of my ribs could this be pulled muscle or how long should I wait?

Not long. Pain in the left rib area could be many things. In general exercise should not be painful or cause pain especially pain that lasts more than a day or so. Certainly cramping/pulled muscles could be the cause, but more serious conditions could be the case such as heart conditions or even a spleen issue. Discussing this with your dr would be a good idea to get a better description and history.
Could be. This certainly could be a pulled muscle. This should start getting better after 1-2 weeks if you refrain from the activity that caused it. However if it does not get better, you should see your doctor to get it checked out to make sure it is nothing more serious.