Raz B Hand Injury -- My Hand Won't Work Right for 3 Months!

B2K singer Raz B is healing nicely from the gruesome hand injury he suffered in China this week, but he tells TMZ it's going to be AT LEAST three months until his hand is functional again.

As TMZ first reported, Raz B accidentally fell through a glass door in his hotel room in Shanghai, slicing his wrist wide open and losing a scary amount of blood.

Raz B tells TMZ he lost count of how many stitches it took to sew him up ... but says doctors will remove his patch work sometime next week.

Raz says he's still experiencing numbness in his fingers ... and doctors have told him it could take at least three months until he regains full functionality.

Once he recovers, Raz tells us he wants to get back to his tour as soon as possible.

Just stay away from the glass doors.