How to repair bend in pewter goblet stem
It is very likely it can just be straightened with no additional treatment. Tin strain hardens ( cold works) very slowly compared to most metals and will stress relieve at room temperature.  According to old references "pewter" ( a k a - Britannia metal ) is not pure tin but contains 7% antimony and 2% copper. But because this is apparently a newer product, one is not sure what the composition is ( I have seen zinc and aluminum novelties called "pewter"). I suggest straightening it, if it cracks it is unlikely to be tin/pewter.