Hello Sathish
Indeed, BPDUs don’t include the VLAN ID in their headers. However, when using PVST, switches know to run STP for each individual VLAN. In other words, each VLAN runs its own separate instance of STP. This is possible because BPDUs are sent inside VLAN-tagged frames. The VLAN ID is included in the Ethernet frame, not in the BPDU itself. So, when a switch receives a BPDU, it can tell which VLAN it pertains to by looking at the VLAN ID in the Ethernet frame.
I hope this has been helpful!
Laz