It is difficult one - since a tyre is being used and could be (I am not saying this has happened) as a result of usage caused the issue.
But, again the law is very clear, items sold to be of satisfactory quality and should last as reasonable time.
If it was something like a TV and suddenly there the screen went even AFTER the 1 year warranty, u can still get it fixed or replace for FREE.
But a tyre, is less so since it is expose to the element - u might struggle to proof it shouldn't have a bulge with after very little use.
The law would still be on your side, but its proofing to the retailer that the tyre was of unsatisfactory quality when u bought it hence resulting in an early bulge.
As Arizona said, DO NOT drive it esp. at high speed!!!
Best, also to check with the retailer if they offer any warranty.
Most NEW tyres should come with some sort of 1 year guarantee, some even offer lifetime repair (obviously they cannot repair a bulge).
I would simply go back to the retailer and see as a gesture of goodwill they will replace it 1st - u never know
If not, then there are all sort of legal help u can sort: Most house insurance and even car insurance come with LEGAL ADVISE for ANY legal matters - u can ask them.
If not, and if u are upto it, put a case together, research the current consumer law and go back to the retailer with it....
Good luck and keep us posted!