Hi , 


The best option to create a validation rule on the Opportunity Object, 

Criteria :   Status = Closed & Current user != Owner || Current User Profile != System Admin  

Throw Error - Once opportunity is closed it can be edited only by Owner or System Admin. 


Here are two approaches to preventing users from editing Closed or Closed Won opportunity records.  The examples below use example profile IDs in the formula syntax.  Note that the IDs used below will vary by organization.

** CLOSED **
The following Validation Rule will only allows users edit closed opportunities if they are assigned to a Profile ID listed (example is System Administrator "00et0000000q111" or Sales VP "00et0000000q222") will be able to edit the Opportunity.
Validation rule syntax:

AND(
PRIORVALUE( IsClosed ) = True,
NOT(OR(
$Profile.Id = "00et0000000q111",
$Profile.Id = "00et0000000q222"))
)


** CLOSED WON **
The following Validation Rule will only allows users edit closed/won opportunities if they are assigned to single profile ID below (example is System Administrator or "00et0000000q111") will be able to edit the Opportunity.

AND(
ISPICKVAL(PRIORVALUE(StageName),"Closed Won"),
NOT($Profile.Id = "00et0000000q111")
)


http://help.salesforce.com/apex/HTViewSolution?id=000005286&language=en_US


Also, See some samples below, 

https://developer.salesforce.com/docs/atlas.en-us.usefulValidationRules.meta/usefulValidationRules/fields_useful_validation_formulas_userroleprofile.htm


Regards,

Ashish