Relation or difference between Input clamp current and Sink current
The buffer output current is the amount it can provide into a load and still maintain the \$V_{OH}\$ and \$V_{OL}\$ specifications.

The amount of current it will actually drive is dependent on the load, in your case a PIC input. (Make sure it is an input and not an output or you will get bus contention).

The input clamp current is the maximum that the PIC can handle if the current were injected (for instance if the voltage on the pin exceeded the supply).

So you can use the buffer and the PIC together without any issues.