Yes, you can invoke a function from the chaincode itself.
The general format to invoke a chaincode is as follows:
stub.InvokeChaincode(chaincodeName, queryArgs, channelName)
But this is used to invoke another chaincode. So if you want to invoke the function by the chaincode itself, you have to modify the above code. If you want to call the chaincode in same channel, leave the channelName parameter empty.
So you can just pass the first two parameters
stub.InvokeChaincode(chaincodeName, queryArgs)
Source: https://github.com/hyperledger/fabric/blob/release/examples/chaincode/go/chaincode_example05/chaincode_example05.go#L90