https://psref.lenovo.com/syspool/Sy...Centre_M725_SFF/ThinkCentre_M725_SFF_Spec.PDF
According to this spec sheet, you're on the highest processor support by the prebuilt. Before you jump in and think the socket should accept Ryzen 3000 and 5000 series processors or APU's, the issue isn't the socket, it's the BIOS that is on the board.
There are multiple threads around the forums where users have asked for a processor upgrade but the BIOS is what's locked by Lenovo, stifling your upgrade process.