Most likely the whitish thing that you have noticed is the Slough which helps in the healing so just don't worry about it until or unless there's increase in pain and swelling or else there's an increase in the temperature of the localized area..As in u get a feeling of the area being warm.
Next Steps
Please maintain a good oral hygiene and don't try to disturb the wound by scraping off the white Slough as it might delay the healing process.Your doctor is the best judge to evaluate the exact condition and please let him know about your doubts in your Next visit which is likely to be in next couple of days.