Using two IF THEN in sql stored procedure

I am trying to create a stored procedure in MySQL Workbench. I need to check if a certain flag is equal to 1. If the flag is equal to 1, then search by FollowupDate else use QuoteDate

IF(qFollowup = 1) THEN
      IF(pFromFollowupDate != '') THEN
      BEGIN
        SET @Main = CONCAT(@Main, '  AND DATE(q.FollowupDate)  >= \'',pFromFollowupDate,'\' ');
      END;
ELSE
IF(pFromDate != '') THEN
BEGIN
  SET @Main = CONCAT(@Main, '  AND DATE(q.QuoteDate)  >= \'',pFromDate,'\' ');
END;
END IF;
END IF;

When I try to apply the changes it says there are syntax errors.