Set off from work last night in the piss-wet soaking rain and after a few yards heard a 'rippling' noise at the back

was a busy one-way street so pulled in at the end of it as soon as poss.
Tyre was flat as a pancake

this will sound a bit anal but the spare wheel/jack has never been used! they are still brand-new from the factory and I kinda want to keep them like that

it's also a space-saver and the alloys are notoriously difficult to remove (stick to hubs) and it was pissing it down sooooo.....I gingerly crept along at 15mph to the Tesco Petrol station (they know me there

) so I've now driven 400mtrs in total at low speed.
Do you think this will harm the tyre wall realistically?
Turns out I'd caught the tyre valve on the curb when I parked yesterday and split it

also turned out the tyre machine at Tesco was out of order so I bought a cheap 12v compressor and pumped the tyre up, also used gaffa tape to bind the tyre valve and went home - did a good job as there was still 20psi the tyre this morning
Going to get the Valve replaced today but do you reckon the tyre will be ok? it's a Pirelli P7 (one I kept as a reserve when I had the Kumho's fitted and then needed again after the suspension scrubbed one rear tyre away).