Great choice, Sumanth. No need to wait. Quitting smoking is a truly great thing to do.
I smoked for 20 years, starting during my freshman year in college. I ran cross-country in high school and it didn't take long after I started smoking to where I couldn't run like I used to. After quitting, running did become easier with time. Replacing smoking with a good habit, like exercise, is a great idea. The main thing is that you commit to not taking another puff, regardless if you pick up another activity or not. With time, you will see that quitting smoking will have a lot of great benefits for you.
Welcome to the site. It is great to have you here.