If as others have said, the plastic lugs have broken, replace the whole steering shaft, it is dangerous and shouldnt be used.
The plastics lugs are not important. They are only there to hold the shaft at the correct length during assembly.
They are important. If they are broken it means the shaft has suffered an impact. The shaft is two piece to allow it to collapse in an impact and not spear the driver. If the shaft has suffered an impact then the likelyhood is that the perforated steering casing will have also collapsed.