It is difficult to tell what would have gone wrong without analyzing the log. However, see if the following documents help
Ref: PSU Opatch conflict check fails with "OPatch failed with error code 73" (Doc ID 861507.1)
Ref: ERROR: "The Oracle Home does not meet OUI version requirement. OPatch failed with error code 73" (Doc ID 729218.1)
Ref: OPatch Failed With Error Code 73 Because Session Is Not Able to Create a Directory (Doc ID 1269454.1)
Vandana - Oracle
can you check $ORACLE_HOME/inventory/ContentsXML/comps.xml for patch 18031726
grep -i 18031726 $ORACLE_HOME/inventory/ContentsXML/comps.xml
comps.xml will get updated when patch is applied. So node1 comps.xml would have been updated for this patch.
Seems comps.xml might have been copied from node 1 to node2 and when Opatch reads patch information at node 2 from comps.xml, it searches for 18031726 patch files. since patch is not applied physically, you will get this error.