IRS says ... How much can I earn and still get SS benefits? If you are under full retirement age for the entire year, we deduct $1 from your benefit payments for every $2 you earn above the annual limit. For 2015, that limit is $15,720. Beginning with the month you reach full retirement age, your earnings no longer reduce your benefits, no matter how much you earn. I'm guessing from age 62 - 67 if you continue trading, you don't take SS early?
It isn't "earned income", so doesn't impact your SS. (That is, unless you are trading via a corporate entity and paying yourself a salary.)
Once you reach full retirement age, both earned and unearned income can affect the portion of your social security check you must pay taxes on. If social security is your only income you probably don't even have to file a return. However if you have additional income, you may have to pay tax on a portion of your social security benefit. Typically up to half the benefit is taxable, but it can be up to 85% taxable depending on your filing status. Single people, in particular, can get hit with 85% of their benefit being taxable. Also, it is good to realize when doing retirement planning that although payments into retirement accounts and social security cease once you've retired, payments into medicare don't stop until you die.