Facing error of "The default schema does not exist." when executing runtime query inside sp using exec()

i have made a runtime query inside a sp and am exceuting the query within the sp using exec(), but when creating the sp i am getting the error

The default schema does not exist.

The SP is:

CREATE PROCEDURE MySP
    @tableName varchar(100)

AS
BEGIN   
    SET NOCOUNT ON;

declare @selectQuery varchar(MAX)

set @selectQuery = 'select * from ' + @tableName

exec(@selectQuery)

end

kindly help