Khalmatov started his senior international career in 2021 when he competed at the 2021 World Judo Championships where he lost to Mongolian Lkhagvajamtsyn Önöbold in the first bout.

At the 2022 European Judo Championships, Khalmatov defeated Italian Angelo Pantano but lost to Lukhumi Chkhvimiani from Georgia in the round of 16.

The 2022 World Judo Championships were not successful for him, since he lost to Mohammad Rashnonezhad from the Refugee Team in the round of 32.

At the 2023 European Judo Championships, Khalmatov won silver after he lost to Luka Mkheidze from France in the final.

In Paris, he defeated Doston Ruziev from Uzbekistan but lost to the eventual Olympic champion Yeldos Smetov from Kazakhstan.