The left side of my scrotum is swelling and/or seems to be filling with fluid the day after an embolization to stop varicocele; is this normal?

Possible, just wait: What you observed and described could be the possibly expected subsequent event after emboliziing gonadal vein attributable to varicocele. So, give time and patience as long as being bearable and slowly getting better day by day although the pace of resolution and the eventual outcome may not be predictable. More? Ask interventional radiologist who performed such task fo you.