Depending on financial goals and horizon of investment (time period), investments can be done in mutual funds, either through lumpsum or SIP method. Also, investing in lumpsum at high market prices for a short term, might NOT end up with a favorable result.
Flexi Cap is an equity fund, with riskometer at 'very high' rating. Similar is Aggressive Hybrid fund with riskometer at 'very high' rating, but from the Hybrid category. So, depending on the time period you would want to hold this investment, a suitable call can be taken. Normally, pure equity or equity related funds are advised to be invested for a minimum period of 3 years (not mandated legally for open ended funds but expected to be followed by investors) to counter the volatility and high risk.