8wk po bunionectomy. Scar tissue build up top of foot. Caused toe drifting. Dr did steroid inj. Less then 24hr ago. Pain has increased since. Normal?

Yes. There can be pain rebound when injected but the steroid gradually will reduce inflammatory pain. Follow up with your surgeon.
STEROID FLARE. It can be; it's called a steroid flare. If he/she is trying to break up scar tissue, probably used a steroid which has these characteristics. It will resolve on its own. Analgesics and ice may help; ice for only 10 minutes/hour. Most importantly, follow your surgeon's advice. Sincerely, Dr. Latva.