NPS is a good option if you want tax benefits. However, if the lock-in period is your primary concern, there are alternative options available. ELSS mutual funds are a good option with only 3 years of lock-in period and also give you tax benefits under Section 80C. 
PPF is another tax-saving choice with a 15-year lock-in period, but you can withdraw a partial amount after 5 years. So managing NPS with these schemes gives you flexibility with both tax savings and less lock-in period.

Congratulations on the maturity of your FD, and it's good that you are investing your money wisely.

Mutual funds and SIPs are the best options, as you can invest in a diversified portfolio and have a low risk factor. Stock Market can give you high returns, but the risk is very high because of the market's unpredictable nature. PPF is an excellent choice for long-term investments and also offers tax benefits. Real estate can also be a good investment option.