It is typical to experience chronic lung pain after a pneumothorax or collapsed lung. You need to check with your doctor to be sure that the pain is not a sign that your lung has collapsed again.
You should progressively engage in more strenuous activity. It is difficult to tell you exactly when you to be 100%. Generally it will take you at least as long as this injury has caused you to be less active. The best rehabilitation for this type of injury will be aerobic activity, like running. Avoid activities that put excessive stress on your chest and raise the pressure within your chest, such as shoveling snow and weight lifting.
What your feeling is absolutely common. No need to worry though. The pain your feeling could very well be some scar tissue rubbing insde your pluera where the chest tube used to be. Especially if your shoveling snow, this will tend to be a bit sore, like with any old injury.
Once the lung is sealed, its all good. Especially if your young. Seeing that you're even running a few miles here and there, I see no need to worry at all!
Andy RRT, CPFT
PW: Do what I did and save the sweat. Have some kid shovel you out for $20 bucks! Ha-Ha!