I hit the tip of my nose 6 months post rhinoplasty could I have caused any harm to my results?

You are still healing after your rhinoplasty and so yes, your nose may be a little more susceptible to damage than usual.  However, the cartilage in the nose is resilient. Its shape doesn’t change easily; that’s why surgeons must break the bone and cartilage to reshape it, rather than just “pressing” it into a new shape.
Keep an eye on your nose tip: If it seems to be swollen or misshapen, then please consult with the facial plastic surgeon who performed your rhinoplasty. Otherwise, you should be fine. I hope this helps.

Dear riionjal,it is impossible to tell without an examination. In case you are concerned, I would suggest you to consult a board-certified plastic surgeon. Daniel Barrett, MD, MHA, MS 
Certified, American Board of Plastic Surgery  
Member, Am. Society of Plastic Surgery

Best to check with your surgeon, as it is possible for things to shift if the hit was severe enough.

It would be very unlikely since cartilage is so elastic but not impossible. If it looks normal, it is almost certainly ok. If it is visibly deformed, you need to see your plastic surgeon. There are some less common variations in rhinoplasty such as repositioning the septum to the midline or the use of strut grafts which might result in a greater possibility of injury with a hit. If you are concerned, just make an appointment so your doctor can see you. Follow up visits such as this are typically free of charge and the reassurance might do you well.