If it is a hematoma (and that sounds quite likely) after a month it should be feeling better, but often still tender. The best thing is to keep moving it (walking a lot) so the blood can still flow and disperse. If the stirrup is still hurting it, take the stirrup off the saddle. I rode bareback for six weeks after I broke my toes.
Hematoma usually aren't serious, but they do take forever to heal. If its still bothering you another month down the line, then worry. But the treatment for a hematoma is rest until it doesn't ache, then move about until it goes down.
Keep up the vitamins, that'll always help. I put my horse's tendon-gel on mine and it really helped.