After foot surgery I had an injection to help the healing process but insurance didn't cover it. Can I deduct the cost as a medical expense?

Yes, medical expenses do not have to be covered by insurance in order to be deductible on your tax return. 

In general, the IRS defines medical expenses as, "the costs of diagnosis, cure, mitigation, treatment, or prevention of disease, and for the purpose of affecting any part or function of the body."

There are some cases where the expense would not be deductible, such as a non-prescription treatment.  

However, be aware that in order to see a tax advantage for claiming the expense you must be using itemized deductions and your total medical expense must be greater than 7.5% of your Adjusted Gross Income (AGI). 

To learn more, see IRS Publication 502.