The 36-year-old striker scored both goals after being introduced as a second half substitute in Blues' 2-1 home win against Wolves on Sunday lunchtime.
"I think I showed I still have a bit left in me," he told Sky Sports.
"People write you off over 30 but I am 36 now and I think I showed I can still do a job.
"It is just nice to get on the pitch. I have not had much game time lately.
"I said to myself I would have to be patient this year. I knew I would get my chance.
"You have to be mentally strong. You have to keep believing you will get your chance.
"It is a short career and I know I am not too far away from retiring.
"I want to play for as long as I possibly can at the highest level and moments like today make me want to play for longer."