After my concussion in boxing, I had to return to lifting in the following time frame

1) 2 weeks into PCS: swimming (light)
2) one month into PCS: normal swimming
3) two months into PCS: stationary biking
3) three months into PCS: normal biking outside
4) three months into PCS: suffered a setback because i was at a loud place for too long
5) four months into PCS: swimming only
6) five months into PCS: stationary biking
7) now it is November, seven months into PCS: I can do weightlifting. Trying to work it up to running

It is a slow process, be patient so you don't suffer setbacks. Don't go all out because your testosterone drives you to do so. (That's how I suffered my concussion lol)