I accidentally ate some non halal chicken, what should I do?

Heres the situation: I went to a restaurant and ordered a "Vegetarian" dish. I have been to that restaurant many times and always have had only "Vegetarian" dishes. The dish I ordered also comes in meat form but I ordered the vegetarian version of it. It was a curry and half way through eating it I saw a piece floating, on checking I found out it was chicken (non halal). I did NOT actually eat/ingest the meat only the curry part but the meat was submerged in the curry. What should I do? I feel horrible, I didn't mean to do it. It was an accident. Will I be forgiven? Are there any specific prayers I can perform?