I think you may need to go to ER to have them check it.
According to the eMedicine article on Hemorrhoid treatment, post-surgical complications include one that involves swelling and pain -
"Acute hemorrhoidal crisis is a rare event that usually requires emergency treatment. The mechanism of action is large internal hemorrhoid prolapse. The sphincter mechanism squeezes, incarcerating the internal hemorrhoids and strangulating them. The resulting spasm causes edema and occasionally thrombosis of the external hemorrhoids. The resulting pain and swelling are dramatic and very painful."
emedicine.medscape.com/article/195401-treatmentpractical advice - take warm sitz baths, clean water only, no soap; liquid diet or very low residue with something like Benefiber or Miralax to keep things very soft; sit on one of those pillows with a hole in the middle.