Japanese Traditional Songs – The Yubikiri Song

• 指 yubi – finger
• 切り kiri – cut; a cut
• げんまん gen man – [probably from 拳骨 genkotsu (fist)]

• うそ uso – lie; a lie
• ついたら tsui tara – If tell (a lie)

• 針 hari – needle, pin
  
• 針千本 hari sen bon – 1000 needles. [the 本 is used to count needles – a thousand 千 to be precise]
  
• 飲ます nomasu – give a drink, cause to drink [same as 飲ませる ]

• 指切った yubi kitta – finger cut

The meaning of this line could be in addition to drinking 1000 needles, the liar will also cut his or her pinkie. However, more likely, it just means "cut" the connection of their fingers. As they say "kitta," people release the pinkie hold.