Can I apply for a new UK visit visa when I have still Valid UK visitor visa?

My exam was on 26th of March and which was cancelled due to this covid pandemic, but I applied for visa on that exam date, now that i have got the 6month visitor visa which is valid till 14th of september, 2021. Now the issue is that the earliest exam that I could book was 10th of october, 2021 and my visa will ve expired by that time.Now i am confused that can I apply for a new visitor visa while still having a valid uk visitor visa. please guide what to do in this situation