weak alar cartilage and a collapsed nostril what can be done this is after a septorhinoplasty.

Over resection of the lower lateral cartilage through a cephalic trim causes weakening of the nostril support and can lead to collapse of the external airway and notching of the alar rim. Correction of this commonly seen deformity can include lateral crural strut grafts which are long, thin cartilage grafts harvested from the septum or rib cartilage placed from the dome and into pockets into the nostrils to help reinforce and reshape the nostril. General ENT specialists may not be well versed in these secondary corrective procedures. 

A rhinoplasty procedure can help with collapsed nostrils  at rest or upon inspiration. Spreader grafts inserted underneath the  concave upper lateral cartilage can help with the nasal valve collapse.   Alar rim grafts will help the nostril rim from collapsing with inspiration. For many examples and more information, please see the video and link below

This can be a problem even in those who haven't had a rhinoplasty, but valving on inspiration after rhinoplasty can occur if steps are not taken to prevent it. You will of course need a full assessment, but your ENT specialist seems to have done that.Strong, flat lateral crura prevent this.  The lateral crura are the parts of the alar cartilages that collapse during inspiration.  If they are strong and straight this helps prevent the problem. There are a number of ways of doing this, most of which mean a cartilage graft, either from elsewhere within the nose or possibly rib.  But it can be corrected.I hope this helps.

I am going to assume that the nasal septum was straightened and the inferior turbinates reduced at the first surgery.  If the nostrils are collapsing then there may be insufficient support from the lateral crura of the lower lateral cartilages.  The first step I take is to see if the airway improves by manually pulling the cheek laterally where it attaches to the nostril and having the patient estimate the degree of benefit.  If the airway improves then I decongest the turbinates with Afrin, wait about 10 minutes, and repeat the maneuver again.  If there is no or little improvement it tells me that the turbinate, not the nostril is the cause.  If there is still substantial benefit with the maneuver after Afrin then I use a small wire loop to pull laterally areas of the nostril to see where the areas of obstruction are.  Once I know that then I can plan where best to apply cartilage grafts (spreader or alar batten, or both; flaring sutures).  I prefer to use ear cartilage to take advantage of its natural curvature and flexibility