John's Conflict of Interest in Stock Recommendation

John is a portfolio manager at an investment advisory firm and has been managing funds for a diverse group of clients. Recently, he made an investment recommendation to buy a specific stock, XYZ Corp, which he believed would provide good returns for his clients. However, John also holds a personal stake in XYZ Corp, as he purchased shares for his personal investment portfolio a month prior to making the recommendation.

Upon reviewing the situation, one of his colleagues raised concern regarding the potential conflict of interest in John's recommendation. Given the situation, what action should John take to ensure compliance with CFA Institute's Code of Ethics and Standards of Professional Conduct?