Nelson provided the update after missing practice Sunday, a day after he was hurt. He walked with a slight limp, and was wearing a wrap around his injured leg.
Nelson initially feared the injury was worse after he was pushed over during a team drill and defensive end Mario Williams rolled up on his leg.
Buffalo coach Chan Gailey expects Nelson to miss four to five days. The Bills get a day off Monday, before returning to training camp in suburban Rochester on Tuesday.
Reserve cornerback Justin Rogers didn't finish practice Sunday after hurting his hamstring.