I opened an SEP IRA account with chase and transferred $500.
Do I need to buy bonds or stocks using this amount this year itself or can I buy bonds after 2 years?
There are no restrictions as to when you can purchase bonds or stocks for money that is properly in a SEP IRA account. You can buy now or let the money sit there and buy in the future.
Why do you ask this question? Is there some doubt as to whether you are able to put money into the SEP IRA account in the first place?
An IRA is a special "bucket of money" that lives on the other side of a tax "island". To move money from one island to another, something happens taxwise. Moving money to the IRA "island" or the nonprofit "island", you get a tax deduction. Moving it from the IRA "island" to a Roth "island" you pay some tax. That happened when you put the $500 into the account. You get a $500 tax deduction for that.
What happens on that island stays in Vegas, as far as the IRS is concerned. They do not care how or when you invest the money in the IRA "island".
That said, there are smart and stupid ways to invest money on the IRA "island". Those vary depending on your age, your relationship with volatility, and market conditions. If someone said "I want to hold off on investing til a year after the election" I wouldn't have a big problem with that under these market conditions.