The incident happened near Corbett Place and Calais View at about 08:30 on Thursday.
Officers are now urging anyone who saw the man to get in touch.
He is described as being in his late teens or early 20s with dark, curly, short hair. He is about 5ft 9in and was wearing a dark top.

12 July 2017 Last updated at 07:06 BST
Can you spot him?
Yes, it's the 130th anniversary of the first Sherlock Holmes book, so it's a pretty good choice.
Sherlock is famous for solving complicated crimes, and now visitors to Maze can put their own detective skills to the test.
They will have to find their way through the maze and collect clues as they go.
Elementary!

Turnout: 394,990 valid votes (42.5%)
Second preference votes are only used if no candidate receives more than 50% of the vote. The top two candidates then receive the second preference votes from their eliminated opponents.
Also see:
South Wales Police is the largest Welsh police force area by population - some 1.2m people live within it.
It covers everything from Swansea to Cardiff and includes Bridgend, Rhondda Cynon Taf, the Vale of Glamorgan and Merthyr Tydfil.
There are 2,937 officers that work in South Wales Police, with 1,746 support staff and 406 community support officers.
The force's chief constable is Peter Vaughan, with Matt Jukes serving as deputy chief constable.
The total force budget for 2016/17 is £258.9m. The precept is £207.85 for band D properties.
That compares to £200.07 in Dyfed-Powys, £220.06 in Gwent and £240.12 in North Wales Police force areas.
The force has current projected savings of £5.4m in 2016/17 with a projected cut in staff numbers of 21.
There were 89,864 crimes recorded in south Wales between September 2014 and September 2015, a rise of 4% on the year before.
Violence against the person rose by 23%, although all police forces apart from one recorded a rise in the category of offences.
Sexual offences rose by 11%, while burglary offences fell by 5%. Theft offences fell by 6%, while criminal damage and arson fell by 1%.
The last annual inspection of police forces by Her Majesty's Inspectorate of Constabulary (HMIC) said South Wales Police was good at preventing crime and antisocial behaviour and had a good understanding of local neighbourhoods.
HMIC said the force is good at identifying and tackling serious and organised crime groups.

Symbols of every event feature on the design, while the London skyline is included with Tower Bridge, the London Eye, the Shard and Big Ben.
The reverse features London Stadium, the championships' venue.
The event takes place from 4-13 August and there will be live coverage across the BBC.
Medals at July's World Para Athletics Championships, taking place from 14-23 July, will be similar, but feature distinctive disability sport equipment such as a prosthetic running leg and throwing chair.
Rather than engraving, the reverse will be inscribed with braille.
For the first time at the World Championships, 'coaches medals' will also be handed out to recognise those who prepare athletes.
Police in Fife are searching for a man who was seen exposing himself in Dunfermline.
[NEXT_CONCEPT]
This is the award-winning Wistow Maze in Leicestershire and this year a very special character is taking over.
[NEXT_CONCEPT]
Labour's Alun Michael has been re-elected as South Wales police and crime commissioner.
[NEXT_CONCEPT]
The World Championships medals that will be won in London this summer have been revealed, with a shape based on the curves of an athletics track.