About the last non-repeated sentence in 爱人是行船人 The Min song mentioned in the title has the following lyrics (conformed to the "guidelines" of 台湾闽南语常用词辞典):


  在阮的心目中
  伊是一个男子汉
  在阮的一生中
  只爱伊一人
  
  伊的船只已经欲出航
  毋知何时才会阁再入港
  虽然装着笑容
  来共伊相送
  阿～～心爱的人
  暗中目箍红
  
  踮故乡真稀微
  孤单一个过日子
  踮海边轻轻来
  叫着伊名字
  
  阮的心肝已经缀伊去
  毋知何时才会阁再相见
  虽然装着笑容
  来共阮安慰
  阿～～心爱的人
  心肝像针威
  
  (Repeat first verse and first "chorus")


With the help of the above dictionary, I get the following Tai-lo:


  Tsāi gún ê sim-bo̍k-tiong
  I sī tsi̍t ê lâm-tsú-hàn
  Tsāi gún ê it-sing tiong
  Tsí ài i tsi̍t lâng
  
  I ê tsûn-tsiah í-king beh tshut-hâng
  M̄ tsai hô-sî tsiah ē koh-tsài li̍p-káng
  Sui-liân tsng-tio̍h tshiò-iông
  Lâi kā i sio-sàng
  Ah~~ sim-ài ê lâng
  Àm-tiong ba̍k-khoo âng
  
  Tiàm kòo-hiong tsin hi-bî
  Koo-tuann tsi̍t ê kuè li̍t-tsí
  Tiàm hái pinn khin-khin lâi
  Kiò-tio̍h i miâ-lī
  
  Gún ê sim-kuann í-king tuè i khì
  M̄ tsai hô-sî tsiah ē koh-tsài sio-kìnn
  Sui-liân tsng-tio̍h tshiò-iông
  Lâi kā gún an-uì
  Ah~~ sim-ài ê lâng
  Sim-kuann tshiūnn tsiam ui
  
  (Repeat first verse and first "chorus")


I render this in English as follows (note that this is not literal because it's supposed to fit the original tune):


  As far as my thoughts go
  He is a hero for me
  As far as my days go
  I'll love him alone
  
  His boat's already about to leave
  I don't know when he can come back on land
  Though I make a happy face
  As I see him off
  Ah~~ he's my one love
  I'm crying secretly
  
  Back home I'm so lonely
  Living my days all alone
  And on the beach I call
  Call his name softly
  
  My heart has gone off to sea with him
  I don't know when I can see him again
  Though I make a happy face
  I now comfort myself
  Ah~~ he's my one love
  (My heart is strong like a needle ??)
  
  (Repeat first verse and first "chorus")


First of all, if there are any glaring mistakes in the above (keeping in mind it must fit the tune), please let me know. This question focuses on the sentence 心肝像针威. Now, 心肝 has a number of meanings, from "heart" to "character" to (in Min) "mind" to "darling", so that's already a choice to make; 像 means "like"; 针 means "needle"; 威 is given as "power" by Wiktionary. Hence my translation in brackets. But what does this mean? Is ui supposed to be 偎 as in this song, with which this would be "Heart like needle cuddle", or in English "My heart feels like a needle is cuddling to it", implying utmost pain due to the needle stinging the heart? But then why do captions get it wrong? Also, I am skeptical of this guess since 偎 is not ui but ue (says Wiktionary at least), so it doesn't rhyme… Maybe it's even another character?
Cross-posted on Quora this morning, and the answer came in soon. I was told "ui" means "prick" (the verb, not the noun), so I turned that into Mandarin 刺, and my reference gave me 揻, with precisely that sentence as an example: 心肝像針揻。Sim-kuann tshiūnn tsiam ui. (心像被針刺一樣。); (other example: 揻一空　ui tst khang(戳一個洞)). So that's it.

Literal translation: My heart feels like pierced by a needle.
Singable translation: A needle's piercing my heart.