Liam Craig's first-half strike gave Saints their first league win over the Tangerines in 13 years.
"We have a big game against Celtic next week. We know it will be difficult. There are a few walking wounded in there," Saints boss Lomas said.
"But it is no coincidence that we had a tremendous away support, they played a big part. For the players to come out and see 1500 away fans makes a big difference. I thought we deserved the three points, especially after the first 15 minutes. Our keeper didn't have a save to make."
Saints midfielder Craig- who has signed a pre-contract with Hibernian - lit up a lifeless opening period in the 38th minute with a fine finish from inside the penalty area.
There was huffing and puffing from both sides in an equally dull second-half but no more scoring as United lost their third straight post-split game.
Craig said: "I want to leave on a high but it (Europa League) is out of our hands, all we can do is keep winning games. If Inverness hang on to third place then they deserve it."
United boss Jackie McNamara, who revealed defender Sean Dillon will go in for an operation on his ankle on Monday, claims his squad is being stretched as the Taysiders stumble towards the end of the season.
The former Celtic and Scotland defender said: "I thought we started the game okay, had a couple of chances and then they came into it.
"We were disappointed with the goal we lost, coming from our throw-in. I also thought we were a bit predictable at times and didn't ask enough questions of their defence or goalkeeper."
- Sports & Recreation
- Liam Craig