On a STANDARD (non RFT) this is extremely dangerous with the possibility of a blow-out.....not something you want happening at high speed
On a RFT tyre (I don't know) could be less dangerous, due to the captive way in which a RFT is held on the rim, and due to the strengthend sidewalls that RFT have
but a bubble especially on an RFT means that the sidewall has been damaged, possibly manufacture fault, or a heavy impact with a pothole/curbstone etc.
If you suspect that it is manufacturing defect, then go back to the tyre dealer that fitted the tyres new, with your invoice, they will notify the manufacturer to investigate, and if determined to be manufacture (non driver induced impact damage) fault, then they will re-imburse you the cost based on the tread remaining, for the replacement of a new trye