All depends on the angle of the screw as well as its positioning. In the middle is good, it can be repaired but if the screw has gone in at a sharp angle it probably won't be fixable. If a guy says 'hmm... yeah It should be ok' then walk away and find someone that can give you a definite answer, its your safety remember!
Get a second verdict, this guy might only be interested in flogging you a new tyre!