Watt moved to the Belgian club on a season-long deal in August in an effort to develop his prodigious talent and earn some regular game time.
Lennon is confident the 19-year-old has a future with Celtic, and hopes Watt will use his time on the continent to mature.
The Scotland U21 star came off the bench to score a brace as Lierse beat Mechelen 3-0 on Boxing Day, much to the delight of coach Stanley Menzo who has been frustrated with the youngster at times this season.
Despite scoring more goals than their Scottish Premiership rivals this season Celtic's forwards have been finding it hard to get on the scoresheet, prompting rumours Lennon may recall Watt in January.
Lennon said: "I'm not of a mind to bring him back just yet. We've loaned him for the year and I'd like him to see that one out.
"We couldn't put him out on loan anywhere else if he does come back so that's not crossed my mind.
"I wasn't aware the Lierse coach has had a pop at him publicly. I'll speak to Tony, see how he's feeling and what the situation is.
"There's an immaturity about Tony and the reason for putting him on loan was we wanted him to sample a different culture and a different type of football.
"If it's not going well then he needs to knuckle down and make it work. The onus is on him.
"He can be a difficult boy at times but there's no malice in him. He just needs to knuckle down and make the most of the opportunity he has.
"When he has finished he will still be part of our plans for the future. There's no question Tony definitely has ability. He's raw and just needs to polish himself off as a fully-rounded figure.
"He's not a man yet. Some players take a bit longer to mature than others - not physically, in a mental aspect as well. But Tony's a good kid."