I swear - this is the first time I've heard of any Polish - Slovakian conflict after WW1. Are you sure you're right?
As far as I remember - after WW1, one of the new states, that emerged out of former Austro-Hungary was Czechoslovakia, not separate Czech Republic and Slovakia (like they're now). So - I think you're referring to Zaolzie, that I've mentioned above.
But - I may be wrong. I'm not a historian, and just after WW1 it was a total mess and kind of a national "kettle" in Central Europe, many nations were fighting each other to create own state and form its best borders. So - I can't exclude, that there were some Polish - Slovakian clashes. I'll try to find something about it.
The Poles moved into Cieszyn only after Slovakia was effectively taken over by the Nazis. It was to protect the Polish citizens from the Germans, not to "steal" land from Slovakia, which for all intents and purposes had ceased to be an independent nation.