Yes, you should have paid estimated taxes, on your $100,000 capital gains, in the first quarter of 2021. Taxes are pay-as-you-go. This means that you need to pay most of your tax during the year, as you receive income, rather than paying at the end of the year.
Regarding what you should pay in, we can't tell you an amount or percent since the amount is dependent on all your income, deductions, filing status, etc. One way to get a good estimate of how much to pay is to use TurboTax.
Additional information: How can I pay my federal taxes?
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