Not all glass pieces are visible in plain X-ray films. The lead content in the glass determins this. Higher the lead content, more is the radio-opacity. Glass from vials and ampoules may not show up on plain films.
As you seem to have pain, it is probable that the foreign body is still in situ.I presume you had shown to a doctor and updated your tetanus immunity status.You have not mentioned when this injury happened.If it is very recent,under supervision,one may decide on a wait and watch policy under antibiotic cover.If the pain persists, a surgical exploration may be warrented.
MB BS, MS, FRCS(Edinburgh)