Hello Rahul
BGP will choose the best path based on the best path selection attributes explained in the following lesson. If you shut down a port and then bring it back up, eventually, all of the attributes will be examined and the best path will be selected. Sometimes BGP takes quite long (on the order of minutes) to reconverge depending on the configuration.
If you want to increase BGP convergence time, take a look at this lesson:
I hope this has been helpful!
Laz