fix(docs): add warning for self bond lock (#998)

Author: dineshpinto

docs/run-node/4-register-validator.mdx

@@ -303,6 +303,13 @@ See [FIP.05](https://proposals.flare.network/FIP/FIP_5.html) for further details
 
 ### Perform the self-bond
 
+:::warning[Self bond & expiry are locked]
+
+Once you set the self-bond and its expiry, both are locked.
+You can't add to or remove the self-bond until the expiry has passed - choose values carefully.
+
+:::
+
 To perform the actual staking transaction (the self-bond), you will use the Flare Stake Tool.
 To retrieve your `Node-ID`, you need to query your running node: