You could try one of these as a temp fix.
https://www.amazon.co.uk/dp/B00C5TJ1MM/ref=cm_sw_r_wa_apa_i_.ZQBCbXE0H912
Could be wrong....but I've always thought repairs were always vulcanised rubber. No metal involved.If you've never seen it before and you've had that tyre a long time, i'd say it's something in the tyre.
Should repair though.