chain grind noises coming from Crank case

[Cali Niwrad]

Hi All,
I come here often to read the forum, but First time commenting. Purchased this dream bike of mine, and was running decent for months, but recently it started a grinding noise in the crank case after a missed shift. The gears are still shifting, and bike is running, but the grinding noise gets loud when down shift to lower speed.

What are your thoughts. Thanks in advance.