When he was younger, Sterling Shepard recalled getting severe headaches and nose bleeds, issues that prevented him from taking part in football camps. The discomfort quickly dissipated and he was fine.

What hit Shepard the past few weeks was much worse. He missed the past two games with migraines that he could not shake, worrying him and forcing him to stay inside, in the dark, nauseous, with blurred vision and sensitivity to light.

“There’s not much you can do about it,’’ Shepard said. “You can pop a few Excedrin, and when the Excedrin doesn’t work then what do you do? It’s not like they can take my brain out and ice it. It’s like I was stuck in a hangover plus a headache. I was just feeling terrible. It was the weirdest thing that ever happened to me.’’

Shepard was able to practice Wednesday without any limitations and should be good to go Sunday, in Oakland, in Geno Smith’s first start at quarterback for the Giants.

OL Justin Pugh missed the past two games with a back injury and said he will try to practice a bit on Thursday.

“If that goes well Sunday’s an outside shot,’’ he said. “I think the following week is a more realistic goal.’’

CB Janoris Jenkins underwent arthroscopic ankle surgery Wednesday, performed by Dr. Robert Anderson in Charlotte, N.C. Jenkins goes directly to injured reserve, ending his season after 11 games. Jenkins has been dealing with an ankle issue for two months and aggravated the problem Thursday. He returned an interception 53 yards for a touchdown in the 20-10 loss to the Redskins and damaged the ankle while diving into the end zone.

The Giants signed defensive tackle Khyri Thornton to replace Jenkins on the roster — the fifth defensive player added to the roster this week. Thornton has 23 games of NFL experience, including four this season for the Lions before he was released Nov. 21. Thornton missed the first six games of the season serving a suspension for violating the NFL’s substance abuse policy.

LB B.J. Goodson missed the past four games with a high ankle sprain. He was back on the field, participated in practice on a limited basis for the first time since going down and out in the second quarter with suffering a high ankle sprain Oct. 22 vs. the Seahawks.

LB Jonathan Casillas (neck/wrist) and Damon “Snacks’’ Harrison (elbow) did not practice. LB Calvin Munson (quad) was a full participant. … DE Romeo Okwara was moved from reserve/injured to an IR/designated for return status. He has been on IR since Oct. 17 with a knee issue. … LB J.T Thomas was waived off IR with an injury settlement.